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As the polyurethane elements and super duplex fasteners are inert/corrosion reisistant in seawater, the only part of the structure requiring corrosion protection is the interface steelwork. This is usually provided by a suitable subsea coating system (e.g. NORSOK, System 7) and either connection to an adjacent cathodic protection system or by attachment of its own dedicated anodes.

 

For particular high temperature applications (i.e. production flowlines) the use of titanium or Alloy 625 Element fasteners may be considered.

 

The polyurethane elements are usually moulded yellow or alternatively orange. Both colours provide excellent visibility when the restrictors are subsea.

 

Typical material properties of polyurethane used to manufacture Bending restrictor elements are outlined below:

 

TYPICAL PHYSICAL PROPERTIES AT 23°C
Property	Test Method	Value	Unit
Shore Hardness	BS 2782 Pt 3	80	°D
Tensile Strength	BS 903 Pt A2	45	MN/m2
Elongation at Break	BS 903 Pt A2	20	%
Heat Distortion Temperature	BS 2782 Pt 1	70	°C
Izod Impact Strength (Notched)	BS 2782 Pt 3	8	KJ/m2
Specific Gravity - cured		1.150	kg/m3